1. Field of the Invention
The invention relates to a mesa semiconductor device having a mesa groove and a method of manufacturing the same.
2. Description of the Related Art
A high power mesa diode is conventionally known as one of mesa semiconductor devices. A conventional mesa diode will be described referring to FIGS. 7 and 8. FIG. 7 is a schematic plan view of a semiconductor wafer where a plurality of conventional mesa diodes is disposed in a matrix. FIG. 8 is a cross-sectional view of FIG. 7 along line X-X, showing a state after dicing along a scribe line DL.
An N− type semiconductor layer 11 is formed on a front surface of an N+ type semiconductor substrate 10. A P type semiconductor layer 12 is formed on the front surface of the N− type semiconductor layer 11, and a first insulation film 23 is formed on the P type semiconductor layer 12. An anode electrode 14 electrically connected to the P type semiconductor layer 12 is further formed. A cathode electrode 15 is formed on the back surface of the semiconductor substrate 10.
A mesa groove 26 is formed from the front surface of the P type semiconductor layer 12 to the N+ type semiconductor substrate 10. The mesa groove 26 is formed deeper than the N− type semiconductor layer 11, of which the bottom is located in the N+ type semiconductor substrate 10. A second insulation film 47 fills the mesa groove 26 so as to cover the sidewall thereof including the PN junction JC of the N− type semiconductor layer 11 and the P type semiconductor layer 12 which are in contact. The mesa diode is surrounded by this mesa groove 26, forming a mesa structure. The scribe line DL of this mesa diode surrounds the mesa groove 26 on its outside.
A mesa semiconductor device is described in Japanese Patent Application Publication No. 2003-347306, for example.
In the conventional example described above, however, since the anode electrode 14 is exposed, water or the like enters the mesa diode from a gap between the anode electrode 14 and the first insulation film 23 to contaminate the mesa diode. Furthermore, the mesa diode is easily damaged physically.
For solving this problem, it is conceivable that a passivation film is further formed from the mesa groove 26 onto the end portion of the anode electrode 14 in addition to the second insulation film 47. In this case, however, the manufacturing process becomes complex by adding a process of forming the passivation film, and the manufacturing cost increases.